Wireless communication networks including Long Term Evolution (LTE) use links between the multiple nodes, such as user equipment and Node Bs, within the system. These links include an uplink portion from user equipment to the Node B or eNode B in the network and a downlink portion from the Node B or eNode B in the network to the user equipment. During a connected mode for the user equipment, the links can utilize a discontinuous receive (DRX) transmission mode. DRX is used in networks such as LTE to allow user equipment to move into a sleep mode while maintaining a connection with the Node B. While in the sleep mode, the user equipment can power down some of operational functions thereby conserving battery power.
A DRX cycle defines the period of an individual time interval between monitoring paging information for a specific user equipment. In other words, the DRX cycle defines the periodic repetition of the on duration followed by a possible period of inactivity. The discontinuous transmission cycle includes an on duration of a given number frames followed by an opportunity for DRX, otherwise known as an off cycle. The user equipment determines it's on duration and off cycle based on stored specific discontinuous transmission cycle length data. The longer the DRX cycle, the longer the user equipment is in a sleep state and before it can check and respond to a paging message. The DRX cycle length is given in number of frames, where 1 frame is usually known to be 1 msec and the on duration is usually set for 3 or 7 frames.
The duration of the on duration and the off cycle is known to be variable. The durations may be set according to a profile set up on the user equipment. Generally, once the durations have been set, the periods are fixed. An off cycle that is too long may result in unnecessary or unacceptable levels of delay in receiving a paging signal. On the other hand, an off cycle that is too short may reduce the operating life of the user equipment's battery.
The on duration timer specifies the number of consecutive downlink frames during which the user equipment shall monitor the physical downlink control channel (PDCCH) for possible allocations. The longer the on duration time is the user equipment has more flexibility, reliability and reduces delay. On the other hand, a longer on duration timer has adverse affects on battery life. Thus, there is a need to consider issues related to the battery life for the user equipment in light of the DRX cycle.
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